But I want to remind you, though you once knew this, that the Lord, having saved the people out of the land of Egypt, afterward destroyed those who did not believe. (Jude 5, NKJV)
Christians need to be continually reminded of the truth we have known (2 Pet. 1:12). Being reminded of the truth we once knew” is a prevention against falling away. Yes indeed, God’s people can fall away. Among God’s people Israel, those who “did not believe” were “destroyed” in the wilderness (Heb. 3:7-11). Although God had saved them out of Egyptian bondage, when they “rebelled,” “sinned,” “did not obey,” they not enter the land of promise due to their “unbelief” (Heb. 3:16-19). Jude uses Israel’s apostasy to warn faithful brethren of false teachers (Jude 3-4, 8). You see, it matters to God what Christians believe and the teachings we accept. False teaching produces false faith. Although we have been saved from the bondage of sin, if we do not faithfully continue in “the faith,” then we become like the wilderness Israelites. And like them, we will be destroyed because of our unbelief.